Measurement of print-to-print register of a multicolour print (also sometimes referred to as “colour register measurement”) is known as such in the art. Such measurement is in particular carried out in the context of multicolour offset printing where the multicolour print typically consists of multiple offset-printed patterns which are juxtaposed on the printed material using multiple printing plates.
Measurement of print-to-print register is not only of interest in the context of one and a same printing process, such as offset printing, but also when the printed material is subjected to different printing processes. Such is the case in the context of the production of security documents, like banknotes, which are typically subjected to multiple printing phases, in particular offset printing and intaglio printing. In this context, it is also of interest to assess and to be in a position to measure and, as the case may be, to correct the print-to-print register between e.g. the offset print and the intaglio print as the relevant print-to-print register has to be kept within acceptable tolerances to meet certain quality requirements.
Print-to-print register is typically measured by using dedicated print register marks or targets which are usually printed in margins outside the effective printed area of the printed material. One example of this measurement principle is for instance the “LUCHS” register measurement system developed by Polygraphische innovative Technik Leipzig GmbH (PITSID—www.pitsidleipzig.com). Such special print register marks or targets have the disadvantage that they require additional space on the printed material, which space is also used for other purposes such as colour measurement. Furthermore, due to their location outside of the effective printed area, it is in effect not possible to measure the actual print-to-print register within the effective printed area of the printed material without compromising or interfering with the design to be printed.
There is therefore a need to improve the known solutions to measure print-to-print register of multicolour prints.